50 ' ORGANOGRAPHY. BOOK I. 



tremities, and are often confounded with the glandular hairs 

 above described, from which they have been well distinguished 

 by Link. According to that botanist, they are either simple 

 or compound ; the former consisting of a single cell, and 

 placed upon a hair acting as a simple conduit, occasionally in- 

 terrupted by divisions ; the latter consisting of several cells, 

 and seated upon a stalk containing several conduits, formed 

 by rows of cellular tissue. They are common upon the rose 

 and the bramble, in which they become very rigid, and as- 

 sume the nature of aculei. For the sake of distinguishing 

 them from the latter, they have been called setce by Woods 

 and myself, but improperly ; they are also the aiguillons of the 

 French. In Hypericum they abound on the calyx and corolla 

 of some species, but do not give out any exudation ; they con- 

 tain, however, a deep red juice within their cells. In some 

 Jatrophas they are much branched ; in many Diosmeae they 

 form a curious hinnid appendage at the apex of the stamens. 



Sessile glands, vemicce, or icarts, are produced upon various 

 parts, and are extremely variable in figure. In Cassias, they 

 are seated upon the upper edge of the petiole, and are usually 

 cylindrical or conical ; in Cruciferous plants they are little 

 rovmdish shining bodies, arising from just below the base of 

 the ovary ; in the leafless Acacias they are depressed, with a 

 thickened rim, and placed on the upper edge of the phyllo- 

 dium ; they are little kidney-shaped bodies upon the petiole 

 of the Peach and other drupaceous plants ; and they assume 

 many more appearances. They are conunon upon the petiole, 

 as in Passiflora ; they are also found upon the calyx, as in some 

 species of Campanula, and at the serratures of the leaves, 

 when they are considered by Roper [De Florihus Balsaminea- 

 rum, p. 1.5.) to be abortive ovules ; and they appear upon the 

 pericarp and the skin of the seed ; in the latter case they are 

 called spongiolcB seminales by De Candolle. They are remark- 

 able in Diorujea muscipula for growing from the mouth of the 

 stomates ; and in Nepenthes for closing up the same organs by 

 forming underneath them. (See page 42.) In the latter 

 plant they are found, moreover, in the form of hard brown 

 concretions, lying beneath the cuticle, at the bottom of the 

 pitchers. In figure they are round, oblong, or reniform, and 



